des加密是对称加密中在互联网应用的比较多的一种加密方式，php 通过mcrypt扩展库来支持des加密，要在Php中使用des加密，需要先安装mcrypt扩展库


下面是加密解密的实例



$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$key = "This is a very secret key";//密钥
$text = "Meet me at 11 o'clock behind the monument.";//需要加密的内容
echo ($text) . "\n";

$crypttext =base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_ECB, $iv));
echo $crypttext . "\n";//加密后的内容

echo mcrypt_decrypt(MCRYPT_RIJNDAEL_256,$key,base64_decode($crypttext),MCRYPT_MODE_ECB,$iv);//解密后的内容


在AES加密算法中通常会用到MCRYPT_RIJNDAEL_128、MCRYPT_RIJNDAEL_192、MCRYPT_RIJNDAEL_256三种，后面的128、192、256代表的是秘钥（也就是加密的Key）是多少bit的，比如使用的是MCRYPT_RIJNDAEL_128，那么用这个算法加密时秘钥长度就是128bit的，比如 $key = 'fjjda0&9^$$#+*%$fada'，是20个字符，那在实际加密的时候只用到前16个字符加密（16*8=128）,不足128bit的php中会用'\0'来补齐。


有的时候做项目对接的时候，可能你用的是Php加密的，而对方用的是java写的，对接的过程中就发现机加密后的内容对方解密不了，这是因为Php跟java在实现这个算法的时候有差别，要想正确加密解密需要两边都做下处理：

PHP:


<?php
class Security {
    public static function encrypt($input, $key) {
        $size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);
        $input = Security::pkcs5_pad($input, $size);
        $td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_ECB, '');
        $iv = mcrypt_create_iv (mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
        mcrypt_generic_init($td, $key, $iv);
        $data = mcrypt_generic($td, $input);
        mcrypt_generic_deinit($td);
        mcrypt_module_close($td);
        $data = base64_encode($data);
        return $data;
    }

    private static function pkcs5_pad ($text, $blocksize) {
        $pad = $blocksize - (strlen($text) % $blocksize);
        return $text . str_repeat(chr($pad), $pad);
    }

    public static function decrypt($sStr, $sKey) {
        $decrypted= mcrypt_decrypt(
            MCRYPT_RIJNDAEL_128,
            $sKey,
            base64_decode($sStr),
            MCRYPT_MODE_ECB
        );

        $dec_s = strlen($decrypted);
        $padding = ord($decrypted[$dec_s-1]);
        $decrypted = substr($decrypted, 0, -$padding);
        return $decrypted;
    }
}



$key = "1234567891234567";
$data = "example";

$value = Security::encrypt($data , $key );
echo $value.'<br/>';
echo Security::decrypt($value, $key );

/*Java:

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
  
import org.apache.commons.codec.binary.Base64;
  
public class Security {
public static String encrypt(String input, String key){
byte[] crypted = null;
try{
SecretKeySpec skey = new SecretKeySpec(key.getBytes(), "AES");
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, skey);
crypted = cipher.doFinal(input.getBytes());
}catch(Exception e){
    System.out.println(e.toString());
}
    return new String(Base64.encodeBase64(crypted));
}
  
    public static String decrypt(String input, String key){
    byte[] output = null;
        try{
            SecretKeySpec skey = new SecretKeySpec(key.getBytes(), "AES");
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, skey);
            output = cipher.doFinal(Base64.decodeBase64(input));
            }catch(Exception e){
        System.out.println(e.toString());
    }
        return new String(output);
    }
  
    public static void main(String[] args) {
    String key = "1234567891234567";
        String data = "example";
         
        System.out.println(Security.encrypt(data, key));
         
        System.out.println(Security.decrypt(Security.encrypt(data, key), key));
         
             
    }   
}*/
